Silicides are compounds of silicon and transition metals. Among the best known silicides are those of molybdenum, titanium, niobium, tantalum, zirconium, uranium, hafnium, tungsten, and the like.
One very useful material is molybdenum disilicide. It is one of the very few commercially feasible materials used in high-temperature heating elements for oxidizing environments. Thus, e.g., U.S. Pat. No. 3,027,331 of Schrewelius discloses the preparation of electrical resistance heating elements from molybdenum disilicide.
One problem with molybdenum disilicide, and the other silicides, is that they are usually very expensive to produce. Thus, for example, in the conventional method for making molybdenum disilicide, molybdenum and silicon are heated at a temperature of from between about 1,400 to about 1,600 degrees centigrade for at least about 6 hours.
The materials used in the conventional method are very expensive. Thus, referring to the 1990-1991 Alfa Catalog (available from Alfa Products, Ward Hill, Mass.), molybdenum powder in the 3-7 micron particle size range (reagent number 10030) costs ninety-eight dollars per kilogram, and silicon powder with a particle size smaller than 325 mesh (reagent 12681) costs one-hundred thirty four dollars per kilogram. The molybdenum disilicide available from Alfa Products (reagent number 11549) costs four-hundred twelve dollars per kilogram.
In addition to being very expensive, the molybdenum disilicide material suffers from other disadvantages. Thus, as disclosed in U.S. Pat. No. 4,704,372 of Watanabe et al., a ". . . sintered body of MoSi.sub.2 alone is low in strength and also extremely brittle at normal temperature . . . ."Furthermore, these molybdenum disilicide bodies have low creep resistance at elevated temperatures.
It is an object of this invention to provide a metallic silicide composition with improved mechanical properties.
It is another object of this invention to provide a metallic silicide composition with improved creep resistance.
It is yet another object of this invention to provide a metallic silicide composition with can be prepared in one step by reaction sintering.
It is yet another object of this invention to provide a relatively low cost process for the preparation of a metallic silicide composition.
It is yet another object of this invention to provide a relatively low cost process for the production of metallic silicide composites.